Overnight Bacon Mushroom Breakfast Casserole

There’s something special about waking up to breakfast that’s already prepped and ready for the oven. This Overnight Bacon Mushroom Breakfast Casserole is one of those recipes that makes busy mornings feel effortless. Crispy bacon, tender hash browns, sautéed onions and mushrooms, fluffy eggs, and melted cheddar cheese come together in one hearty casserole that’s perfect for holidays, brunch gatherings, or even a cozy weekend breakfast. The best part? You can assemble everything the night before, so all you have to do in the morning is pop it into the oven while everyone enjoys a cup of coffee.

Leftovers reheat beautifully for quick breakfasts throughout the week.

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Why You’ll Love This Recipe

• Make-ahead convenience saves time on busy mornings.
• Perfect for Christmas morning, Easter brunch, Mother’s Day, or family weekends.
• Loaded with savory bacon, potatoes, mushrooms, onions, and cheese.
• Feeds a crowd with very little effort.
• Easily customizable with your favorite vegetables or cheeses.

Ingredients

• 1 pound bacon
• 1 tablespoon butter
• 2 onions, chopped
• 2 cups fresh mushrooms, sliced
• 4 cups frozen hash brown potatoes, thawed
• 1 teaspoon salt
• ¼ teaspoon garlic salt
• ½ teaspoon ground black pepper
• 4 large eggs
• 1½ cups milk
• Pinch of dried parsley
• 1 cup shredded cheddar cheese

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How It Comes Together

• Preheat your oven to 400°F and lightly grease a 9×13-inch baking dish.
• Cook the bacon in a large skillet over medium-high heat until crisp. Transfer to a paper towel-lined plate, then crumble or chop into bite-sized pieces.
• In a separate skillet, melt the butter and cook the onions and mushrooms until softened and lightly browned.
• Spread the thawed hash browns evenly into the prepared baking dish.
• Season with the salt, garlic salt, and black pepper.
• Sprinkle the cooked bacon over the potatoes, followed by the sautéed onions and mushrooms.
• In a large bowl, whisk together the eggs, milk, and parsley until well combined.
• Pour the egg mixture evenly over the casserole.
• Sprinkle the shredded cheddar cheese over the top.
• Cover tightly with foil or plastic wrap and refrigerate overnight.
• Remove the casserole from the refrigerator about 30 minutes before baking.
• Bake uncovered for about 60 minutes, or until the center is fully set and the top is golden brown.
• If you’re baking immediately instead of refrigerating overnight, bake for approximately 45 minutes.
• Allow the casserole to rest for 10 minutes before slicing and serving.

Tips for Success

• Thaw the hash browns before assembling for even cooking.
• Cook the bacon until crispy so it stays flavorful in the casserole.
• Let the casserole sit at room temperature for about 30 minutes before baking if it has been refrigerated overnight.
• Test for doneness by inserting a knife into the center—it should come out clean.
• If the top browns too quickly, loosely cover with foil during the final 15 minutes of baking.

Variations

• Add diced bell peppers for extra color and sweetness.
• Stir in chopped spinach for added vegetables.
• Use Monterey Jack, Colby Jack, Swiss, or Pepper Jack cheese.
• Swap bacon for cooked breakfast sausage, turkey sausage, or diced ham.
• Add a pinch of smoked paprika or cayenne pepper for a little extra flavor.

What to Serve With It

• Fresh fruit salad
• Yogurt parfaits
• Buttermilk biscuits
• Cinnamon rolls
• Orange juice
• Coffee or hot tea

Storage

• Store leftovers covered in the refrigerator for up to 4 days.
• To reheat, microwave individual portions for 1 to 2 minutes or warm larger portions in a 325°F oven until heated through.
• This casserole also freezes well. Wrap tightly and freeze for up to 2 months. Thaw overnight in the refrigerator before reheating.

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Overnight Bacon Mushroom Breakfast Casserole

Prep Time 20 minutes

Chill Time 8 hours

Servings 8

Ingredients

• 1 pound bacon
• 1 tablespoon butter
• 2 onions, chopped
• 2 cups fresh mushrooms, sliced
• 4 cups frozen hash browns, thawed
• 1 teaspoon salt
• ¼ teaspoon garlic salt
• ½ teaspoon black pepper
• 4 eggs
• 1½ cups milk
• Pinch dried parsley
• 1 cup shredded cheddar cheese

Instructions

1. Grease a 9x13-inch baking dish.

2. Cook bacon until crisp. Drain and crumble.

3. Sauté onions and mushrooms in butter until tender.

4. Spread hash browns into the baking dish.

5. Season with salt, garlic salt, and pepper.

6. Add bacon, onions, and mushrooms.

7. Whisk together eggs, milk, and parsley.

8. Pour over casserole.

9. Top with cheddar cheese.

10. Cover and refrigerate overnight.

11. Remove from refrigerator 30 minutes before baking.

12. Bake at 400°F for 60 minutes, or until set.

13. If baking immediately, bake for about 45 minutes.

Recipe Notes

Great for holiday breakfasts and brunch.

Easily customize with your favorite vegetables or cheeses.

Leftovers reheat beautifully for quick breakfasts throughout the week.